Display systems

ABSTRACT

A poster display system for displaying a plurality of different images which includes an image grid with interlaced strips from the various images, masking grid adjacent the image grid having spaced apart masking strips alternating with spaced apart window strips, a mounting system for mounting the image grid and the masking grid for movement relative to one another, a drive mechanism for producing relative movement between the image grid and the masking grip between successive display positions in which the window strips of the masking grid are aligned with image strips of a particular image, the image strips of the other images being obscured by the masking strips, and compression means for urging opposite edge portions of the image grid and of the masking grip towards each other whereby the image grid and the masking grid become curved and the image grid and the masking grid are brought into intimate contact with one another under pressure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to poster display systems and to methods ofdisplaying poster images.

2. Description of Related Art

It is often desired to display more than one poster image at aparticular site and there already exist poster display systems in whichthe poster image is displayed on a series of juxtaposed elongateelements of polygonal cross-section. One face of each element carries arespective part of the poster image and the image displayed can bechanged by rotating all of the elements in unison so that they eachpresent another face. Such display systems involve the use of amultiplicity of polygonal elements each of which must be rotated duringuse of the systems and to each of which must be attached respectiveparts of each poster image. Thus the manufacture of such a system isexpensive and the changing of the set-up of the system to enable adifferent set of poster images to be displayed is cumbersome andexpensive.

It has been proposed to provide a poster display system for presenting aplurality of different images by mounting a masking sheet over a posterimage sheet and moving the masking sheet small distances relative to theposter image sheet. The poster image sheet is formed with a multiplicityof image strips with adjacent strips defining portions of differentimages. The masking sheet has alternate opaque and transparent strips soas to reveal selected ones only of the poster image strips. In oneposition of the masking sheet relative to the image sheet, strips of afirst image remain exposed while other image strips are concealed behindopaque strips of the masking sheet. In another position of the maskingsheet relative to the image sheet strips of the first image areconcealed behind opaque strips whilst the image strips relating toanother image that were previously concealed behind the masking stripsbecome exposed. Provided the width of the masking strips is not toogreat, a human eye will fill in the masked parts of the image and see anentire poster image. The image seen will, however, vary according towhich image strips are exposed. Thus the display system may be used todisplay a plurality of unrelated static images, or a plurality ofclosely related images which, when displayed in the correct sequence,provide an animation, as for example proposed in U.S. Pat. No.3,918,185.

For the proper functioning of a poster display system of the kind justdescribed, in which image strips relating to a plurality of posterimages are provided on a common poster image sheet, it is very importantthat the relative positions of the poster image sheet and the maskingsheet are very precise. That requirement applies and is relativelysimple to meet if only two images are included on the poster image sheetbut is more onerous if more images are included. Furthermore, it is verydesirable that it should be easy to replace one poster image sheet byanother so that a different set of images can be displayed by thesystem. Further still, it is very important that the poster image sheetand the masking sheet maintain overall contact with each other betweenthe surfaces of the composite material upon which the grids are printed.

SUMMARY OF THE INVENTION

Such requirements have proved very onerous and prevented widespreadcommercial use of such display systems.

According to the present invention there is provided a poster displaysystem for displaying a plurality of different images, the systemcomprising

(a) an image grid carrying a first set of image strips comprising amultiplicity of first strips spaced apart from one another andpresenting different regions of a first image, and a second set of imagestrips comprising a multiplicity of second strips spaced apart from oneanother and presenting different regions of a second image, said secondstrips being distributed over the grid between the said first strips;

(b) a masking grid adjacent to the image grid and carrying a set ofmasking strips comprising a multiplicity of masking strips spaced apartfrom one another and a set of window strips comprising a multiplicity ofwindow strips spaced apart from one another, said window strips beingdistributed over the grid between said masking strips;

(c) a mounting system for mounting the image grid and the masking gridfor movement relative to one another;

(d) drive means for producing relative movement between the image gridand the masking grid between a first display position, in which saidwindow strips are aligned with said first image strips and said secondimage strips are obscured by said masking strips, and a second displayposition, in which said window strips are aligned with said second imagestrips and said first image strips are obscured by said masking strips;and

(e) compression means for urging opposite edge portions of the imagegrid and of the masking grid towards each other whereby the image gridand the masking grid become curved and the image grid and the maskinggrid are brought into intimate contact with one another under pressure.

The use of further compression of the image grid or the masking gridenables them to be brought into close proximity as a result of thesubstantially complete exclusion of air between these grids, and thiscan result in particularly good registration of the window strips of themasking grid with image strips of the image grid, thereby enabling onlyimage strips of one image and no other to be viewed at a time.

The image grid preferably carries three or more sets of image strips. Itis then possible to have three or more images displayed sequentially bythe system. The more sets of image strips that are provided, the greaterthe width required for the masking strips relative to the image strips.As a result, accurate mounting of the masking strips relative to theimage strips, which can be facilitated by the present invention, becomesmore advantageous.

Using a masking grid having masking strips alternating with windowstrips, the width of each window strip may be less than one fifth of thewidth of adjacent masking strips and a good image can still bedisplayed. It is advantageous that the masking strips between adjacentwindow strips have widths of less than about 2 mm so that the imagesappear continuous to the eye.

The width of each window strip is preferably less than the width of eachimage strip with the respective window strip is aligned. Such extrawidth of image strip provides a small tolerance for the relativepositions of the window strips and image strips, and it also allows foroblique viewing of the display.

Although the image grid may form one face of a rigid body of substantialthickness, it is preferably formed on a flexible sheet whichadvantageously has a thickness of less than 1 mm and more particularlyof less than 0.5 mm. The image strips are preferably printed on theimage grid.

The masking grid should at least be translucent and preferablytransparent. It is also preferred that the masking strips be printed onthe masking grid. Forming the image strips and the masking strips byprinting is very simple and modern printers can print such strips withsufficient accuracy.

The masking grid and the image grid are preferably made from the samematerial so that they will expand and contract in a similar way inresponse to temperature changes and the like. These two grids preferablyhave a low coefficient of expansion.

It is generally preferred to arrange the image grid and the masking gridwith their respective printed faces immediately adjacent to each otheras this can enable the accuracy of positioning the image strips and themasking strips to be improved and problems caused by oblique viewing canbe reduced.

Whilst it is possible to have an intermediate translucent sheet orsheets between or laminated to the image grid and the masking grid, itis preferable to have these grids in direct contact with one anotherwith substantially no air between them. The exclusion of air frombetween the grids not only enables them to be brought into contact withone another, it also tends to keep them in contact with one anothersince the grids can only separate as a result of air entering betweenthem at their edges. If one or both grids are laminated with alaminating film to protect the ink used to print the respective grids,the lamination film is preferably not more than 13 μm thick.

In addition to using compression to bring the image grid and the maskinggrid into intimate contact, systems in accordance with the presentinvention can include additional means for increasing such contact.Electrically charging one of the grids is a particularly suitable methodof achieving this. Employing the inherent static properties of the imageand masking grids to attract one grid to the other is another suchmeans.

Systems in accordance with the present invention preferably includeadjustment means for setting up the relative positions of the image gridand the masking grid in a first display position. Such adjustment meanspreferably allow an operator to carry out fine adjustment of therelative positions of these grids after the installation of a new imagegrid, and it is preferred to use a screw-threaded adjuster element toeffect such adjustment.

The adjustment means preferably includes means for altering thepositions of a drive member for moving the moveable grid, and the drivemeans by which it is driven, relative to a member to which the staticmember is fixed. The drive member may be a rotatable cam which ispreferably detachable without dismantling the display unit, it beingparticularly convenient to be able to change the cam and the gridswithout dismantling the whole system. Thus the position of the axis ofrotation of the cam is preferably adjustable using adjustment means.

The material from which the image grid and/or the masking grid are madecan also be significant. Preferably they are of a plastics material andmore preferably polyethylene terephthalate or a polycarbonate. Anespecially preferred material is sold under the trade mark Melinex, thegrade Melinex 506 being used in the specific embodiments of displaysystems in accordance with the present invention which are describedherein.

Systems in accordance with the present invention preferably includemeans for lighting the image grid from behind both the image grid andthe masking grid and this can be provided by providing a pathway fornatural light and/or at least one artificial light source.

It might be thought that the masking grid would have to be in front ofthe image grid, but we have found that these grids can be mounted eitherway around, it being preferred to use back lighting when the image gridis nearest to the viewer. The mounting arrangement can, therefore,enable the two grids to be mounted with either in front. However, it isespecially preferred to use a mounting arrangement for detachablymounting the image grid in front of the masking grid when the curve ofthe grids is concave as seen by a viewer, but behind the masking gridwhen the curve of the grids is convex as seen by the viewer. Replacementof the image grid can then be relatively simple.

The drive means can be attached to either the masking grid or to theimage grid. The grid not so attached remains static.

It has been found that by curving the image grid and the masking grid,the retention of overall contact between the two adjacent faces of thesegrids can be greatly improved. Such a curve can be achieved by fixing aclear base panel, made of the same or similar material, and of the sameor similar thickness as that of the image grid and the masking grid,along two opposite edges within a display housing to an angled sectionusing clamping bars of an appropriate material. The clear base panel canthen be fixed so that it forms a natural curve when the display housingis laid horizontally on its back.

When in this position, the lowest part of the curve formed by the clearbase panel can, for example, be between 5 and 50 mm lower than its fixededges. Once the base panel has been fixed in position, for example usingclamping bars, adjustable compression bars of an appropriate materialcan then be positioned between the two clamping bars. A secondary clearpanel can then be positioned between the two compression bars.

The curved width of the secondary clear panel is preferably a fewmillimeters less than the curved distance between the two compressionbars when these two bars are fully adjusted away from each other.However, the curved width of the secondary clear panel is wider than thecurved distance between the two compression bars when they are fullyadjusted towards each other. The compression bars can therefore beadjusted to meet the corresponding and parallel edges of the secondaryclear panel and then further squeezed together providing a compressiveforce upon the secondary clear panel forcing it into the curve of theclear base panel. In this manner, the curved clear base panel and thecurved secondary clear panel become sufficiently rigid to retain acoherent curve when the display housing is raised into an upright andvertical position.

The masking grid, which has a width which is less than the curveddistance between the compression bars and thereby allowing lateralregistration of the masking grid in relation to the image grid, isplaced over the secondary clear panel and fixed to this panel byadhesion or by the use of bolts along its top or bottom edge through thesecondary clear panel to the clear base panel.

The image grid, which also has a width which is less than the curveddistance between the compression bars but is greater than the width ofthe masking grid, is placed over the curved masking grid and it isattached to a mechanism for moving it up and down relative to themasking grid. Lateral registration of the image grid relative to themasking grid can then be achieved using off-set cams positioned eitherside of the image grid towards the edge of the image grid furthest awayfrom the mechanism. These cams can then be rotated and fixed in positiontouching opposite side edges of the image grid once the latter has beenlaterally registered with the masking grid. Vertical registration of theimage grid relative to the masking grid using the mechanism has beenpreviously described.

If desired, the image grid and the masking grid can be interchanged sothat the masking grid is in front of the image grid. In such a case, theimage grid is preferably fixed to the secondary clear panel or throughthis panel to the base panel, and the masking grid is then positionedbetween the off-set cams and fixed to the drive mechanism.

If desired, a front sheet of a clear material can be placed tightlybetween the compression bars and fixed through the static grid and thesecondary clear panel to the clear base panel. The height of themoveable grid is then preferably sufficiently less than that of eitherthe clear panels or the static grid to avoid the fixings of the clearpanels and the static grid.

If a separate diffusion panel is not incorporated into the displayhousing to diffuse light from lamps, either of the clear panels behindthe grids or the rear grid itself can be made from a semi-opaquematerial.

The compression bars can be used in place of the cams to achieve lateralregistration of the grids though this generally requires very accuratecutting of whichever is the moveable grid.

If required, illumination for the display can be positioned on theconcave or the convex side of the curved clear panels and grids with thedisplay unit being viewed from the other side of the curved clear panelsor grids.

If required, the drive mechanism can be fixed to the top panel of thedisplay housing, or to the base panel of the display housing. When thedrive mechanism is attached to a side panel of the display housing, sothat the compression bars are at the top and the bottom of the displayhousing, a solid bar of clear material should in general be fixedtightly between the compression bars in front of the concave curve ofthe clear panels and grids so that this solid bar bends to match thecurve of the clear panels and grids. Such a bar should be placed betweenboth ends of the compression bars, and thus two such bars should beused.

If required, whichever grid is placed over the secondary clear panel canitself be attached to the protruding stud on the drive mechanism,thereby becoming the moveable grid. The grid placed over the moveablegrid then becomes the static grid which is attached to the clear basepanel through the secondary clear panel.

Whichever grid is the moveable grid, it should in general be wider thanthe static grid to allow retention of registration if off-set cams areused to act on the moveable grid.

If required, either grid can be placed directly on to the clear basepanel and the secondary clear panel can then be omitted, and indeed theclear front panel can also be omitted. Furthermore, the static grid canreplace the clear base panel, and the secondary clear panel can bereplaced by the moveable grid. Thus if the clear front panel is alsoomitted, only the image and masking grids would form the semi-rigidviewing area. In this latter case, the moveable grid would need to becut very accurately as the compression bars become the means of keepingthe moveable grid in linear registration with the static grid.

To overcome friction between the moveable grid and the compression bars,which would require greater torque from the drive motor, the compressionbars can be attached directly to the moveable grid. Compression can thenbe applied directly to the compression bars, for example using off-setcams or adjustable circular bearings attached to the angled section.These off-set cams or adjustable bearings can also be used to effectlinear registration between the image grid and the masking grid.

If the images made up of image strips on the image grid making up therespective images differ from each other only slightly, it is generallyunnecessary for the image strips of the image grid to be wider than thetransparent strips of the masking grid in order to achieve a smoothvisual sense of animation of the image, especially if the grids aremoved fairly rapidly relative to each other. In addition, when the imagestrips of the image grid and the transparent strips of the masking gridare of substantially the same width, the number of image strips that canbe displayed, for example in an animation, can be increased compared toarrangements where the image strips are wider than the transparentstrips because the number of image strips masked by each masking stripof the masking grid can thereby be increased. As will be appreciated,the more images that make up an animated sequence the smoother andlonger an animated sequence can be. However, if the image strips arenarrower than the width of the transparent strips, the animation effectwill usually appear blurred.

By way of example, the opaque strips on a masking grid of A2 size can beat least 2.00 mm with the image strips and the transparent strips of themasking grid each being as narrow as 0.10 mm. It is then possible toprovide an animated sequence of twenty images, each image varyingslightly from its adjacent images, by obscuring nineteen consecutivesets of image strips using masking strips on the masking grid which are1.90 mm wide. The twentieth image strip is then visible from behind orin front of the transparent strips of the masking grid.

In some instances it might be desirable to dwell for a longer period oftime on, say, the final image of an animated sequence, in which case thelast two image strips of each set of image strips can be identical orcan have a width greater than the window strip. Cams controllingmovement of the moveable grid will in general need to be adaptedaccordingly. For example, if each image is displayed through the maskinggrid for 0.25 seconds, the whole animated sequence from the first to thetwentieth and back to the first image would last for 10 seconds, i.e. atotal of forty images times 0.25 seconds per image. In this manner, ananimated display can be achieved, for example a bird in flight oradvertising graphics that appear at first to be moving away from theviewer and then towards them.

As the size of the masking grid and the image grid is increased, thewidths of the opaque strips on the masking grid can often be increasedas the viewing distance increases. However, the width of the imagestrips on the masking grid do not necessarily have to be increased inthe same proportion, and the number of image strips that make up ananimation sequence can thereby be increased as a result of using widermasking strips.

Embodiments of display system in accordance with the present inventionwill now be described by way of example with reference to theaccompanying diagrammatic drawings.

BRIEF DESCRIPTION OF THE FIGURES OF DRAWINGS

FIG. 1 is a sectional side view of a mechanism for effecting relativemovement between the image grid and the masking grid of a firstembodiment of system of the present invention;

FIG. 2 is a front view of the mechanism of FIG. 1;

FIG. 3 is a sectional view along line III—III of FIG. 2;

FIG. 4 is a partially cut away view of a first embodiment of system inaccordance with the present invention;

FIG. 5 is a perspective view, to an enlarged scale, of the portion ofFIG. 4 defined by the broken lines X-Y and W-Z;

FIG. 6 is a similar view to that of FIG. 5 of a second embodiment havingdifferent compression means;

FIG. 7 shows the cam used with the embodiments described with referenceto the preceding FIGS.;

FIG. 8A shows a cut away portion of an image grid positioned over amasking grid;

FIG. 8B shows a similar view to that of FIG. 8A but with the maskinggrid over the image grid;

FIG. 9 shows an alternative form of cam;

FIGS. 10A and 10B show an image grid and a masking grid respectivelyhaving image strips and window strips of the same width;

FIG. 11 is a perspective view of a portion of a slider arrangement of ayet further embodiment;

FIG. 12 is a front view of the embodiment of FIG. 11;

FIG. 13A is a section through an alternative slider arrangement to thatshown in FIG. 11;

FIG. 13B is a perspective view of the slider arrangement of FIG. 13A;

FIG. 14A is a section through a further alternative slider arrangementto that shown in FIG. 13A;

FIG. 14B is a perspective view of the slider arrangement of FIG. 14A;and

FIG. 15 shows a masking grid over an image grid which include means forobtaining registration between the grids.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 to 3, a drive mechanism is shown which has a fixedrear plate 1 and a front plate 2 movably mounted on the rear plate 1.The front plate 2 has a horizontal, forwardly projecting, top flange 3and it is secured on each side using slide bearings 4A and 4B in amanner (not shown in detail in the drawings) which facilitates precisevertical sliding of the plate 2 relative to the rear plate 1. The rearplate 1 has a horizontal, forwardly projecting top flange 5 whichextends over the front plate 2 and a tension spring 6 (shown in FIG. 1)is connected between the plates 1 and 2, thereby biasing the front plate2 upwardly. A bearing roller 7 is mounted on the rear of the front plate2 and it is biased upwardly by the spring 6 into contact with arotatable cam 8 in front of the rear plate 1. The cam 8 limits upwardmovement of the plate 2 and it thus defines the position of the frontplate 2 relative to the rear plate 1. A stud 31 projects forward of theplate 2.

The cam 8 is mounted on an output shaft 9 of a motor 10 whichincorporates as a unit a motor and reduction gearing. Rather thanmounting the motor 10 directly on the rear plate 1, it is mounted in aposition that is finely adjustable relative to the rear plate 1 as willnow be described.

An adjustable arm 12 is pivotally mounted at one end by a pivot 13 tothe rear plate 1 and it is finely adjustable at the other end by anadjusting mechanism 14 which, when operated, causes limited pivotalmovement of the arm 12 about the pivot 13. The motor 10 has twomountings, the first being pivotal on the rear plate 1 coincident withthe pivot 13, and the second being on a rod 15 which is behind the rearplate 1 and the arm 12. The adjusting mechanism 14 causes limitedpivotal movement of the arm 12 about the pivot 13 and, when it does so,it imparts the same pivotal movement to the motor 10 thereby causing theshaft 9 on which the cam 8 is mounted to move about the pivot 13. Sincethe shaft 9 is at substantially the same vertical level as the pivot 13,the arcuate movement of the shaft 9 and the cam 8 is effectivelyvertical for small amounts of pivoting. An opening 17 in the rear plate1 provides the necessary freedom of movement for the rod 15 to moverelative to the plate 1.

The adjusting mechanism 14 consists of a vertical shaft 18 connected atan upper end to the rear plate 1 and at a lower end to the arm 12 aswill now be described more fully.

In the region of the shaft 18, the rear plate 1 is partially cut awayand portions 19A, 19B and 19C are bent out of the plane of the plate 1,portions 19A and 19C projecting rearwardly and portion 19B projectsforwardly (see FIG. 3). The upper end of the shaft 18 (not shown in FIG.2) passes in front of the portions 19A and 19C and to the rear of theportion 19B, it being screw-threadedly in those portions. In the regionwhere the arm 12 is connected to the lower end of the shaft 18 it issimilarly formed with bent portions 20A and 20C which project forwardsand portion 20B which projects backwards. The lower end of the shaft 18passes behind the portions 20A and 20C and in front of portion 20B, theshaft 18 being rotatably mounted in the portions without any axialmovement. A knurled disc 22 fixed to the shaft 18 midway along itslength enables a user to rotate the shaft 18, and compression springs 23on each side of the knurled disc 22 between the disc 22 and the portions19C and 20A respectively prevent the shaft 18 from rotating except whenthe disc 22 is positively moved by the user.

When the shaft 18 is rotated, the screw-threaded engagement of the shaftwith the portions 19A, 19B and 19C of the rear plate 1 causes the shaft18 to move axially relative to the rear plate 1 thereby moving the endof the arm 12 to which the shaft 1 is connected in a substantiallyvertical direction to pivot the arm 12 about the pivot 13.

Referring to FIG. 4, clamping bars 69 and adjustable compression bars 71within the display housing 43 are attached to the angled section 67 (seeFIG. 5). A clear base panel 68 is located under the compression bars 71and it is fixed to the angled section 67 by clamping bars 69. Thearrangement of a front clear panel 74, an image grid 30, a masking grid25 and a secondary clear panel 73 laid over the clear base panel 68 canalso be seen.

All of the clear panels 68, 73, 74 and the masking grid 25 are cut tothe same length, this being indicated by lines 76 and 77, and they eachhave a slot 78 cut out of them to allow for movement of the singlecentral stud 31 which projects forwards from the mechanism 79 and towhich the image grid 30 is attached.

The image grid 30 is shorter than the clear panels 68, 73, 74 and themasking grid 25 to ensure that as the image grid 30 is moved up and downit is not blocked by fixings 80 that pass through the clear base panel68, the secondary clear panel 73, the masking grid 25, and the clearfront panel 74 to hold the masking grid 25 in position between thesecondary clear panel 73 and the moveable image grid 30. Lines 76 and 81indicate the top and bottom of the image grid 30 when in its highestposition, and the broken lines 82 and 83 indicate its lowest position.

Lower side slots 84 cut from the front clear panel 74 allow off-set cams85 fixed to the compression bars 71 to be swivelled to touch the sidesof the image grid 30 and to keep the image grid 30 in lateralregistration with the masking grid 25. Vertical registration between thetwo grids 25 and 30 is effected by the adjuster 22 forming part of themechanism 79 which has previously been described.

FIG. 1 is a side view corresponding to that of FIG. 4 along broken line86-87 of FIG. 4, FIG. 1 showing the angled section 67 (see FIG. 5) andthe relative positions of the clear base panel 68, the secondary clearpanel 73, the masking grid 25, and the clear front panel 74, plus theimage grid fixed to the stud 31, the image grid being sandwiched betweenthe masking grid 25 and the clear front panel 74. Also shown is how afixing 80 passes through the clear base panel 68, the secondary clearpanel 73, the masking grid 25 and the clear front panel 74 to fix themasking grid 25 in position.

As can also be seen from FIG. 1, the image grid 30 is cut shorter at apoint 88 so that it is not blocked by the fixing 80 when the image grid30 is moved up and down. A spacer 89 between the masking grid 25 and thefront clear panel 74 allows free movement of the image grid 30.

When the masking grid 25 and the image grid 30 form the semi-rigidviewing area, registration between these grids can be facilitated byretaining the compression bars so that they act on the moveable grid.Linear registration can then be achieved by adjusting the compressionbars to ensure that the image strips on the image grid 30 are parallelto the strips on the masking grid 25 whilst applying sufficientcompression to ensure total overall contact between the respectivegrids.

Referring to FIG. 5, a “T” section bar 66 is attached to the interior ofthe display housing 43 to allow the angled section 67 to be set inposition. The clear base panel 68 is attached to the angled section 67by a clamping bar 69 and also to an opposing angled section (not shown)by bolts passing through apertures 70 (see FIG. 4). An adjustablecompression bar 71 is positioned on the clear base panel 68 and it isheld lightly in place by bolts which pass through apertures 72 (see FIG.4) in the compression bars 71 and they screw into the angled section 67through the clear base panel 68.

The secondary clear panel 73 is placed on the clear base panel 68, andthe adjustable compression bar 71 is pushed downwardly and inwardly asindicated by the arrow 71 x so that the secondary clear panel 73 iscompressed between the adjustable compression bar 71 and the opposingadjustable compression (not shown). The bolts passing through theapertures 72 are then tightened to secure the adjustable clamping bars71 in position.

FIG. 6, which is similar to FIG. 5, shows the static grid, in this casethe masking grid 25, attached to an angled section 67 by the clampingbar 69 in a similar manner to that described with reference to FIG. 5.Circular adjustable bearings 130 which can be adjustably fixed towardsor away from the clamping bar 69, as indicated by arrows 131, act uponthe compression bar 71A which is attached directly to the movable grid,in this case the image grid, 30 to compress the moveable grid 30 intooverall contact with the static grid 25. By adjusting the circularbearings 130, appropriate linear registration can also be achievedbetween the two grids. If required, a clear sheet 74 can be positionedbetween the compression bars 71A to protect the moveable grid 30.

As the compressive force is increased to keep the grids together, so thestatic quality of the material used to make the grids tends to become ofless value as an additional means of maintaining overall contact betweenthe grids.

If required, the off-set cams or the circular bearings 130 can be usedto exert a compressive force directly to the moveable grid 30 to keep itin contact with the static grid 25. In such a case, the compression barsare usually unnecessary. Also in such cases it can be more desirable toeffect parallel registration between the two grids by attaching a singlebracket to the moveable grid, this bracket being adjustably attached toanother bracket or block attached to a slideable plate of the mechanismfor moving the associated grid. The bracket attached to the slideableplate is then preferably attached at as great a distance as possiblefrom the protruding stud to which the moveable grid is attached. Themoveable grid can then be attached to the protruding stud on theslideable plate using circular bearings to allow the moveable grid toswivel at the point at which the moveable grid is attached to theprotruding stud. If required, the static grid can be sandwiched betweena clamped clear or semi-opaque sheet and the moveable grid to which thecompressive force is applied.

The cam used in the embodiments of FIGS. 1 to 6 is shown in FIG. 7, and,as can be seen, the periphery of the cam 8 is divided into a pluralityof arcuate portions 8A to 8F, each defining an arc of a circle centeredon the axis or rotation of the cam 8 and having a radius R_(A) to R_(F).At the junction between adjacent arcs are inclined ramps 65. There aresix arcuate portions shown in FIG. 7, but particular image grids andmasking grids may have different numbers of arcuate portions, forexample eight sets of arcuate portions with four sets of image strips.

During use of the illustrated display systems, the cam 8 is rotated bythe motor 10 and, as it rotates, the bearing roller 7 rests against andremains in contact with the bottom of the peripheral surface of the cam8 due to the bias of the spring 6. The vertical position of the roller 7is then determined by the radius of whichever portion 8A to 8F of thecam periphery is in contact with the bottom of the cam 8, and thedifference in radius between adjacent cam portions corresponds to thecenter-to-center spacing of adjacent image strips as shown, for examplein FIGS. 8A and 8B.

An effect of one image fading into another can be achieved by reducingthe incline or increasing the decline of the steps 65.

The cam 8 shown in FIG. 7 will result in the images changing almostimmediately and then remain for a given length of time. However, if theinclination of the steps 65 is considerably decreased and thedeclination of the steps 65 is considerably increased, for example sothat the steps 65 are about one third of the lengths of the arcs 8A-8F,the images displayed will appear to fade into the next which will thenappear for a shorter period of time.

FIG. 8A shows a cut away view of an image grid 30 positioned over amasking grid 25 in a system as described with reference to the precedingdrawings. If these two grids are set up with this relative dispositionwith the roller on one of the portions 8A to 8F, rotation of the cam 8of FIG. 7 through one eighth of a revolution will result in the roller 7moving exactly the distance required to move the image grid 30 relativeto the masking grid 25 by the exact width of one of the image strips,image strips 49B, 50B, 51B and 52B then becoming aligned with windowstrips 58F, 59F, 60F and 61F respectively.

Since movement of the roller 7 takes place in steps rather thangradually as it rolls over successive inclined ramps 65, the image gridis moved accordingly.

Using a cam 8 with six arcuate portions 8A to 8F which form two groupsof three, the first three in turn increasing in radius and the secondthree in turn decreasing in radius, if the cam 8 revolves in a clockwisesense, the image grid 30, will first be moved by three steps downwardlyfrom the first image visible through the masking grid as the cam 8 isrotated, and then three steps upwardly as it completes a revolution backto the first image. Each step brings the next of the four sets of imagestrips into alignment with the window strips 58F, 59F, 60F and 61F ofthe masking grid 25, and it then reverses the sequence, by which timethe cam 8 has completed a single revolution.

As will be appreciated, the cam 8 can be rotated continuously at aconstant rotational speed and the individual strips of the image grid 30will then be viewed for the time taken for the cam to effectapproximately one eighth of a rotation of the cam 8.

If it is desired to display one of the images on the grid 25 for alonger period than the others, the cam 8 can be provided with a longerarcuate portion so that the roller 7 remains in contact with the cam 8for a longer period of time with that portion than on others. In suchcases it is generally preferred to have diagonally opposite long arcuateportions.

A viewer of the display is usually unaware of the way in which the imagegrid 30 is moved relative to the masking grid 25, the viewer simplyseeing a first image which, as the bearing roller 7 passes over one ofthe inclined ramps 65, changes smoothly into a second image, and so on.

It is, of course, desirable that the masking strips 53E to 57E are nottoo thick as this could adversely affect the resolution of the display.However, masking strips with a width of up to about 1.5 mm are generallysatisfactory, but a noticeable reduction in resolution can be observedif the width of these strips is much wider than this. By way of example,the masking strips 53E to 57E can be 1.4 mm wide with the image stripsbeing 0.2 mm wide, the center-to center spacing of the masking stripsbeing 1.6 mm with that of the image strips being 0.4 mm. 12.5% of theimage is then displayed through the window strips. In this case, the cam8 will have adjacent arcuate portions 8A to 8F which differ in radius by0.4 mm.

In the case just described, the image strips are twice as wide as thewindow strips, only one half of each image strip therefore beingdisplayed. However, even in this case, the overlap of the image stripsby the opposing edges of the windows in the masking grid is still only0.1 mm which can be regarded as the tolerance in positioning therespective strips relative to each other. The image grid and the maskinggrid therefore need to be printed, positioned and moved very accurately.It will also be appreciated that any separation of the masking grid fromthe image grid of even less than 0.1 mm can have a markedly adverseeffect on the performance of the system, and especially when the systemsare viewed other than from directly in front.

Although FIG. 8A shows only relatively few image strips and maskingstrips, it will be appreciated that in practice a multiplicity of stripswill be used. For example, the display area can be up to 0.7 m wide ormore and up to 1.0 m high or more, and it is obviously important thatthe image grid and the masking grid be maintained in contact with eachother throughout this area and that differences in expansion betweenthese grids is kept to a minimum.

The arrangement of grids shown in FIG. 8B is substantially the same asthat described with reference to FIG. 8A, but the masking grid 25 is inthis case on top of the image grid 30.

As will also be appreciated, it is possible to move the image grid andto keep the masking grid stationary or to move the masking grid and keepthe image grid stationary, and in either case, the image grid can bebehind or in front of the masking grid.

While the embodiments described above use vertical movement of one gridrelative to the other, it will be appreciated that the grids can bemoved relative to each other horizontally or in a sideways direction. Ina yet further alternative, the relative motion between the grids can bein a vertical direction, but with a drive mechanism below the gridsrather than above them.

FIG. 9 shows an alternative eight sided cam 104 having eight arcuate camsurfaces 105N to 112N which subtend equal angles to and are convextowards its center. The respective ends 114P to 121P of the arcs 105N to112N are each 2.00 mm further away from the center 113 than are thecenters 112Q to 129Q of the surfaces 105N to 112N. Thus when cam 104 isused in place of the cam 8 described in relation to FIG. 7, the maskinggrid 25A or the image grid 30A (see FIGS. 10A and 10B) controlled by themechanism in the manner described in relation to FIGS. 1 to 3 is moved2.00 mm down and then 2.00 mm up as the periphery of the cam 104 movesin a clockwise sense over the bearing 7 of the mechanism 79 fromposition 126Q to 117P and then on to position 125Q.

Further rotation of the cam 104 results in the bearing 7 being forceddownwardly again to arc end 116P, and so on. In this manner, as cam 104rotates by one eighth of a revolution, the masking grid 25A or the imagegrid 30A are moved by rotation of the cam 104 and will at first fall2.00 mm and then rise by 2.00 mm.

Referring to FIG. 10A, each image strip 90C to 94E of the image grid 30Ais 0.20 mm wide, and since image strips B to J of each set 90 to 94 areobscured by opaque strips K95 to K99 of the masking grid, whichthemselves are each 1.80 mm wide, only image strips A90 to A94 arevisible through transparent strips L100 to L103 which are themselves0.20 mm wide. A similar situation applies with regard to FIG. 10B wherethe image grid 30A and the masking grid 25A are identical to those inFIG. 10A but the image grid is on top of the masking grid 25A ratherthan on top of it.

Each of the 0.20 mm wide image strips 90C to 94E shown in FIG. 10A, or90A to 94G shown in FIG. 10B, will then briefly appear twice adjacent tothe corresponding transparent strips 100L to 103L of the masking grid25A, once as the masking grid 25A or the image grid 30A rises, and thenonce as it falls.

Using the cam 104 with the image and masking grids of FIGS. 10A or 10B,if the cam 104 revolves once every forty seconds, the resultinganimation sequence will be five seconds long from the first image to thetenth image and back to the first image again. This results from eachsequence being one eighth of the time taken for a full revolution of thecam 104.

As an alternative to the compression and slide system described withreference to FIGS. 5 and 6, FIG. 11 shows the clamping bar of FIG. 5replaced by a slide housing 69B to which a static grid is attached, forexample a masking grid 25. The bearings 130 of FIG. 5 are replaced by aself-lubricating plastic slider 130A to which the moveable grid 30 isattached, the slide housing 69B being fixed to the angled section 67.

Studs 132 fixed to and projecting from the upper surface of theself-lubricating plastic slider 130A correspond with accurately punchedholes along the side edges of the moveable grid 30 so that when themoveable grid 30 is held in position by the projecting studs 132, it iscompressed into the static grid 25 when the static grid 25 and themoveable grid 30 are concave, the compressive effect being achieved byensuring the distance between the punched holes along one side of thegrid and those along the other side is greater than it would be if thesepunched holes were positioned to hold the grid so that it lay along thecurve of the other fixed grid without being compressed into the fixedgrid. However, if the grids 25 and 30 are convex, the static grid 25 iscompressed into the moveable grid 30, again by ensuring the distancebetween the fixings holding the static grid in position are appropriateto ensure the compressive force is effective.

Referring to FIG. 12, the static grid 25 is longer than the moveablegrid 30, thereby allowing the static grid 25 to be attached to the slidehousing 69B at points 133 without blocking movement of the moveable grid30. To provide a firm backing to facilitate wiping of the grids 30 and25, and to remove air pockets between them, a sheet of clear orsemi-opaque material, say 3 mm thick, can be compressed between the twoslide housings 69B to create a rigid curve matching that of the grids 30and 25. However, great care should be taken to ensure that the changingcurvature of the clear or semi-opaque material caused by expansion andcontraction produced by temperature changes does not affect movement ofthe moveable grid 30, for example by pushing the static grid 25 againstthe moveable grid 30 with such force that the moveable grid 30 is jammedagainst the static grid 25 and thus cannot move.

The upper surface of the self-lubricating plastic slider 130A to whichthe projecting studs 132 are attached projects outwardly of the slidehousing 69B, for example by 300 μm if the static grid 25 attached to theextended upper surface of the slide housing 69B is 250 μm thick.

For greater accuracy of movement of the moveable grid 30, theself-lubricating slider 130A can be replaced by an arrangement of linearor roller bearings at each end of both slide housings 69B, the linear orroller bearing at one end of the slide housing being joined to the otherat the other end of the slide housing by an aluminum bar to whichprojecting studs 132 are fixed corresponding to the holes punched alongthe side edges of the moveable grid 30.

The moveable grid 30 can then be moved by spindles 134 controlled bylinear stepper drive mechanisms 135A and 135B fixed to one end of eachof the self-lubricating sliders 130A. The drive mechanisms 135A and 135Bare controlled by a control board 136, and they can be arranged to drivethe spindles 134 repeatedly up and down in appropriate increments, forexample four increments of 0.40 mm in the case of a quadruple imagesystem, three increments of 0.50 mm in the case of a triple imagesystem, and a single up and down movement of 2.00 mm in the case of ananimated system incorporating ten images each made up of image strips0.20 mm wide.

The self-lubricating slider 130A shown in FIG. 11 is moved by the lineardrive mechanisms 135A and 135B, and the slide housing 69B remainsstatic. However, with the alternative profiles of slide housing 69B andself-lubricating slider 130B shown in FIGS. 13A and 13B, the slidehousing 69B is moveable by the linear drive mechanisms 135A and 135B andthe slider 130B remains static. The slide housings 69B are attached bybrackets 137 to the spindles 134 which are driven by the linear drivemechanisms 135A and 135B, the self-lubricating slide 130B being fixed tothe angled section 67.

The window strips of the masking grid will then usually need to becentered along the center lines of the image strips of the image grid,and this can be effected using the linear drive mechanisms 135A and 135Bto move the associated spindles 134 sufficiently to achieveregistration. If the image strips of the image grid are not parallelwith the window grids of the masking grid, the drive mechanism on oneside of the moveable grid is then adjusted accordingly. Any verticalmovement required to bring about registration of image and window gridswhich are parallel but not otherwise in registration can then beeffected by moving both sides of the moveable grid by the same amountusing the drive mechanisms 135A and 135B.

Movement of the moveable grid relative to the static grid to displayimages can then be effected using equal steps produced by the lineardrive mechanisms 135A and 135B under the control of the control board136. Extra steps can be incorporated into the drive sequence to takeaccount of back-lash in the drive mechanism that can occur when thedriving force changes direction.

FIGS. 13A and 13B show an alternative slide housing 69B andself-lubricating slider 130A, the slide housing 69B being attached tothe linear drive mechanism 135 using brackets 137 attached to thespindles 134, and the self-lubricating slider 130A being fixed to theangled section 67.

FIGS. 14A and 14B show a yet further alternative arrangement of slidehousing 69B and self-lubricating slider 130A which is similar to that ofFIGS. 13A and 13B but has different profiles for the slide housing 69Band the self-lubricating slider 130A, in particular to provide a groovein the angled section 67A in which a portion of the studs 132 extendingbelow the slide housing 69A can run freely.

FIG. 15 shows an arrangement of a masking grid 25 overlaying an imagegrid 30 which include means for obtaining registration between thewindow strips of the masking grid 25 and the individual image strips ofthe image grid 30, the masking grid 25 having been moved to the left toshow the image strips below.

The masking grid 25 shown in FIG. 15 has opaque strips Ei to Evii andwindow strips Fi to Fvii, and the image grid 30 has image strips Bi toDviii.

The window strip Fiv, which is between adjacent masking strips Eiv andEv, has a portion G near to the edge of the masking grid which isnarrower than at its center and narrower than the window strips betweenthe other masking strips.

An edge portion of the image grid 30 beneath the masking grid 25 hasfour window strips AW, BW, CW and DW centered along the center lines offour adjacent image strips AV to AD, these being positioned so that thenarrow portion of the window strip Fiv coincides with the windows AW,BW, CW and DW of the four adjacent image strips AV to DV when therespective sets of image strips A to D are in registration with thewindow strips Fi to Fvii of the masking grid 25. Registration of thewindow strips Fi to Fvii of the masking grid 25 with the respectiveimages of the image grid 30 can then be effected using a photocell todetect light passing through the narrow windows in both grids, and thiscan also be used to control the relative upward and downward movement ofthese grids during normal operation of the system.

The use of a photocell with narrow window strips at the edges of themasking and image grids to control the linear drive mechanisms 135A and135B can enable a particularly accurate positioning of these gridsrelative to each other and it can be used to control the number of thesteps taken between successive images to compensate for backlash in thedrive mechanism or for minor dimensional inaccuracies in the grids.

As will be appreciated by those skilled in the art, registration of theimage grid with the masking grid, both vertically and, to ensure theimage strips are parallel to the window strips, horizontally, can beeffected using arrangements of photocells, for example which respond topositional information determined from the opposite edges of the imageand the masking grid such as have been described for the grids withreference to FIG. 15.

Poster display systems in accordance with the present invention can beused in a wide variety of applications, for example:

1. as retail outlet window displays, the system in accordance with theinvention being suspended against the window of the retail outlet andrelying on external, natural ambient light to backlight the poster or onelectric illumination directed from inside the retail outlet whichbacklights the poster images so that they can be viewed from outside theretail outlet;

2. as illuminated display case accessories in which the display systemis positioned within the case to be backlit by a light source in thecase;

3. as edge-lit display accessories in which the display system ispositioned against the front face of an edge-lit display;

4. as controllable partition systems in which,the partition can betransparent or opaque, the image grid itself possibly being in the formof a masking grid to make the partition opaque when the window strips ofthe masking grid are obscured by what amount to masking strips of theimage grid; and

5. as a vending machine accessory in which the display system ispositioned within the machine so that is can be seen by potential users.

What is claimed is:
 1. A poster display system for displaying aplurality of different images, the system comprising (a) an image gridcarrying a first set of image strips comprising a multiplicity of firststrips spaced apart from one another and presenting different regions ofa first image, and a second set of image strips comprising amultiplicity of second strips spaced apart from one another andpresenting different regions of a second image, said second strips beingdistributed over the grid between the said first strips; (b) a maskinggrid adjacent to the image grid and carrying a set of masking stripscomprising a multiplicity of masking strips spaced apart from oneanother and a set of window strips comprising a multiplicity of windowstrips spaced apart from one another, said window strips beingdistributed over the masking grid between said masking strips; (c) amounting system for mounting the image grid and the masking grid formovement relative to one another; (d) drive means for producing relativemovement between the image grid and the masking grid between a firstdisplay position, in which said window strips are aligned with saidfirst image strips and said second image strips are obscured by saidmasking strips, and a second display position, in which said windowstrips are aligned with said second image strips and said first imagestrips are obscured by said masking strips; and (e) compression meansfor urging opposite edge portions of the image grid and of the maskinggrid towards each other whereby the image grid and the masking gridbecome curved and the image grid and the masking grid are brought intointimate contact with one another under pressure.
 2. A system accordingto claim 1, wherein the compression means applies a further force toopposing edge portions of the masking grid or to opposing edge portionsof the image grid whereby the masking grid and the image grid becomecurved and in intimate contact with each other under greater pressure.3. A system according to claim 1, wherein the image grid and the maskinggrid are curved by the compression means so that they are convex asviewed from the front of the system.
 4. A system according to claim 1,wherein the image grid and the masking grid are curved by thecompression means so that they are concave as viewed from the front ofthe system.
 5. A system according to claim 1, wherein the image grid isin front of the masking grid as seen by a viewer of the system.
 6. Asystem according to claim 1, wherein the image grid is behind themasking grid as seen by a viewer of the system.
 7. A system according toclaim 1, wherein the opposite edge portions of the image grid or themasking grid are attached to slides for facilitating relative movementbetween the image grid and the masking grid.
 8. A system according toclaim 7, wherein the slides comprise linear slides within a slidehousing.
 9. A system according to claim 8, wherein the image grid or themasking grid is attached to the linear slides and the other of saidgrids is attached to the slide housing.
 10. A system according to claim1, wherein the drive means comprises at least one stepper motor.
 11. Asystem according to claim 10, wherein the drive means comprises twostepper motors each of which being arranged to move opposite edges ofeither the image grid or the masking grid to produce said relativemovement.
 12. A system according to claim 11, wherein the stepper motorscan be actuated moved separately or together to effect registrationbetween the image grid and the masking grid.
 13. A system according toclaim 11, wherein the stepper motors can be actuated together to effectchanging of the images.
 14. A system according to claim 1, wherein theimage grid includes more than two images.
 15. A system according toclaim 1, wherein the image grid includes sufficiently large number ofimages whereby operation of the system produces the effect of animation.16. A system according to claim 1, wherein the image strips of the imagegrid are of substantially the same width as the window strips of themasking grid.
 17. A system according to claim 1, including at least oneoptical sensor for controlling the drive means to effect registration ofthe window strips of the masking grid with image strips of respectiveimages on the image grid.